Improving　the　performance　of　silicone　rubber　(SiR)　for　cable　accessories　is　the　key　to　the　safety　and　reliability　of　high-voltage　direct-current　(HVDC)　transmission.　In　this　article,　the　effects　of　zirconia　nanoparticles　(nano-ZrO2)　on　the　electrical　and　mechanical　properties　of　SiR　were　investigated.　Nano-ZrO2　at　different　mass　fractions　was　doped　into　SiR　matrices.　Then,　a　series　of　experiments　was　carried　out　to　evaluate　the　performance　of　the　modified　SiR　in　terms　of　tensile　strength,　breakdown　strength,　and　space　charge　characteristics.　The　results　showed　that　both　the　mechanical　and　electrical　properties　of　the　modified　SiR　improved.　The　tensile　strength　and　the　breakdown　strength　increased　significantly　with　the　mass　fraction　of　nano-ZrO2,　maximally　increasing　by　21.3%　and　15.4%,　respectively.　In　addition,　the　incorporation　of　nano-ZrO2　into　SiR　inhibited　space　charge　accumulation　and　accelerated　the　dissipation　of　the　charges.　Nano-ZrO2　also　improved　the　degree　of　cross-linking　of　the　modified　SiR,　resulting　in　a　more　compact　interior　structure.　The　synthetic　effect　of　the　improved　structure　and　interfaces　facilitated　by　the　nanoparticles　may　be　the　origin　of　the　improved　properties　of　the　SiR　nanocomposites.